Heating dielectric materials and apparatus therefor



June 3, 1952 M. BATIUK ETAL 2,599,360.

HEATING DIELECTRIC MATERIALS AND APPARATUS THEREFOR Filed Dec. 16, 1948 2 $I-lEETS-SHEET l will MEL. WEE/i 27 Bail/k Hazazzzan EEhfvsjy June 3, 1952 M. BATIUK ETAL 2,599,360

HEATING DIELECTRIC MATERIALS AND APPARATUS THEREFOR Filed fies. 16, 1948 2 SHEETS-SHEET 2 Mf -AL 775E527 Bah/k 1 225177027 EEhfI/EQ Patented June 3, 1952 HEATING nmLno'rmo MATERIALS AND APPARATUS THEREFOR Martin Batiuk and.

HarmonG'. Shively, Akron,

Ohio, assign'ors to The B..-F,. -Goodrich Com"- pany; New York, York N. Y., a corporation of New Application December 16, 1948, Serial No. 65,604

9 Claims.

This invention relates to heating a dielectric materialby the use of a high frequencyalternating electrostatic field'andparticularly to the heating of a liquidcontaining material such as a vulcanizable'foamed rubber latex.

It is an object of thisinvention toprovide a method and apparatus for heating uniformly a dielectric material which releases a liquid or a vapor when heated.

It is a further'object to provide a. method and apparatus forheating such a material while it is advancing continuously througha high fre quency alternating electrostatic field. I I I In addition, it is an object of this invention to further increase the 'nu ber' of possible applications of 'a high" frequency electrostatic field for heatingdielectric'materials.

Hereto'fore attempts to heat liquid-containing materials, andespecially those materials which evolve'a large quantity of moisture when heated bymeans of a highfrequen-cy alterhatingelectrostatic field'have met with many difficulties.

When heating such a material as an aqueous dispersion of rubbery material, for example foamed latex, a great quantity of water is driven w off in the form of water vapor. The surrounding air thenbecomes heavily laden with moisture which will 'ofc'ourse condense on anyccol surface such as that of the electrodes employed to create the electrostatic field, interfering with their proper functioning. Water dripping from the electrode will result in arcing of the high frequency current along the path. of the falling I drops of water with a resulting burned spot in the material being heated. In addition, if the drop of water strikes the materiallbeing heated it tends to cool it locally, resulting in uneven heat treatment. p

The heating method and apparatus herein dis.- closed maybe used in heating any material which might release a liquid,.vapor,.or gas when heated. However, to. illustrate the invention a detailed description of heating avulcanizablefoa-med rubber latex will be given. 7 I v In Fig. l a side elevation of the heating apparatus is shown;

Fig. 2 is a detailed view ashorting, bar';.'

Fig. 3 is aplanview of the heating apparatus;

Fig. 4.,is .a. sectional view along line 4-4. of

The apparatus comprises basically a. topelectrode l; l1. and abottom el'ectrodelZ for es.- tablishing {high frequency-field; a. conveyor-belt 3.:for introducing the material to be treated into of a tuning: stub with 2: 11 the field; and a heating system for the 'top electrode. The top electrode is divided into two sections l0, II' to provide greater flexibility in. control of the temperature and rate of heatingduring the initial and final heating stages of: the material. The=t0p electrode l:0,.- His made of brass manifolds i5, I5 and brass connecting tubes l6, l6. Angle irons 2'6,- 26 are secured to the assembled top electrode by. means of bolts and nuts 21, 2? and clamping members 28, 28, the angle irons in turn being-secured .to insulators 34, 34 by means of bolts and nuts 35, 35'. The insulators, which support the whole top electrode, are suspended from hangers.I4,.;"l4 "by means of pins 33,33. The clamping members. also secure a fine mesh copper screenLZS againstthe lower side of thebrass pipes I 6, l6;- .Thereforethe effective parts-of the top electrode), lil'iare the way they serve to conduct the: heating medium to and from manifolds-I 5 without permitting excessive loss of. high frequency energy.

The outer ends of: the choke coils I 1', 11,21, '21 are connectedto the lowerelectrode. l2 by copper straps 32', 37, 38,. 38. in order togrounds those points on thesteam. and condensate 1ine's.'...The choke coils 17,: I1, 21, 2t may bemade :of any metal which is. a good conductor such as copper, silver, or brass. Byiusing such: metals which have low electrical. resistance the. power loss' is kept correspondingly low. A flexible": tube ofirnbher or other electrically resistant.material-may also be usedsince practically no current will flow through them and of course the power loss Will againbelow. 1 m "3 Another means of providing anfimpedance 'to the flow of the high frequency current through the steam inlet ,andoutlet lines isshoWn-in'F'ig. 2

in which a loop-of tubing; in the form-of a tuning stub l! is employed to replace the :coil described above. The tuning stub 4! acts aszfaresonant section of atransm-ission line, and-is: provided with a shorting bar; 42 slidable alongzthezloop. to

permit variation v,in: ,,the resonance-of thaloop on stub. This tubing stub may: beef: any tubu:

lar, electroconductive material such as copper, silver, or brass. The shorting bar 42 may be of the same materials and is free to slide along the length of the loop to allow tuning to resonance with a particular frequency. This tuning stub M may be substituted for one or more of the choke coils l1, l1, 2|, 2| to accomplish the same results; that is, the tuning stub will (1) convey the steam or condensate, and (2) act as an impedance to the flow of high frequency current through the steam line. If desired, both the tuning stub and a choke coil may be used in combination to achieve the desired effect. That is the tuning stub may be connected in parallel with the coil and tuned in the same Way as is done when the tuning stub is used alone. When such a combination is used, either the tuning stub or the coil or both may carry the steam or steam condensate as the case may be.

The bottom electrode consisting of metal plate 23 is mounted on a wooden bench 22. An endless conveyor belt [3 having deckle strips 24, 24 is provided to carry the material to be heated between the opposing electrodes. Belt 13 may be made of fabric-reinforced rubber or any other suitable construction. The belt is mounted on roll 32 which is drivenby chain and sprocket drive 43, and passes over idler roll 3! with its upper reach overlying bottom electrode 12 and in slidable contact therewith. A hopper 36 is positioned above one end of the belt l3 to deposit the unvulcanized foamed latex upon the belt uniformly. A source of high frequency alternat ing current, indicated diagrammatically at 29, is connected to the opposing electrodes by means of leads 30, 40.

In employing the apparatus of this invention for heating and vulcanizing foamed latex, the latex foam containing conventional compounding ingredients such as a gelling agent, vulcanizing agent, accelerator, etc. is deposited from hopper 36 upon the upper surface of belt !3 in a layer of substantially uniform thickness and is carried by the moving belt between the opposed electrodes. Steam is admitted from line It! into the manifolds and tubes of top electrode I0, II to heat the electrode to a temperature at least about 5 F. above the temperature of the ambient atmosphere, or above the dew point of the atmosphere. A high frequency alternating electrostatic field is generated between top electrode H], II and bottom electrode !2 by means of oscillator 28, the length of choke coils l'i, 2| or the position of the shorting bar 42 on the loop or stub 4| being adjusted to minimize loss of electrical energy through the steam lines. As the foamed latex advances under the first section I0 of the top electrode it is heated to about 140 F. to cause the foam to gel; during this heating stage only a small proportion of the aqueous medium in the latex is evaporated. The gelled foam is then advanced on belt l3 under the second section 12 of the top electrode and is heated to about 210 F. During this second heating stage the foamed latex is vulcanized. The finished product 39 is stripped from the belt -l3 at the driven roll 32.

Obvious variations and modifications may be effected within the spirit and scope of the invention as defined in the appended claims.

We claim:

1. In an apparatus for heating a dielectric material, a pair of opposed, spaced electrodes, one being an upper and the other a lower,-said upper electrode comprising a pairof opposed manifolds with interconnecting tubes and an inlet and outlet, means for maintaining said dielectric material between and spaced from said electrodes, means for establishing a high frequency alternating electrostatic field between said electrodes, and means for passing a heating medium through said upper electrode to heat it above the temperature of the surrounding atmosphere comprising an impedance means connected in shunt relation between said opposed electrodes at each said inlet and outlet.

2. The apparatus of claim 1, wherein the impedance means comprises a choke coil of electroconductive tubing through which said heating medium passes.

3. Apparatus of claim 1 wherein the impedance means comprises a loop of electroconductive tubing through which said heating medium passes.

4. The apparatus of claim 3 in which means comprising a shorting bar slidable along said loop is provided to vary the impedance thereof.

5. Apparatus of claim 1 wherein the impedance means comprises a choke coil of electroconductive tubing in parallel with a loop of electroconductive tubing having a shorting bar slidable thereon to vary the impedance thereof.

6. Apparatus for progressively heating a dielectric material comprising a pair of opposed spaced elongated electrodes, conveyor means for advancing said dielectric material between and spaced from said electrodes, at least one of said electrodes comprising a pair of opposed manifolds with interconnecting tubes and an inlet and outlet, means for passing a heating fluid through said inlet, said manifolds, said interconnecting tubes and said outlet to heat said electrode, means for providing an impedance to the fiow of high frequency current through the heating fluid inlet and outlet, said impedance means electrically connecting said opposed electrodes in shunt relation, and means for establishing a high frequency alternating electrostatic field between said electrodes.

7. Apparatus for progressively heating a liquidcontaining dielectric material comprising a pair of opposed spaced elongated electrodes, one being an upper and the other a lower, means for establishing a high frequency alternating electrostatic field between said electrodes, conveyor means for advancing said dielectric material between and spaced from said electrodes, the upper electrode comprising a pair of opposed manifolds with interconnecting tubes and an inlet and outlet, and means for passing a heating fluid through said upper electrode with little loss of high frequency energy comprising a choke coil of tubing, through which said heating fluid passes, connected to each said inlet and outlet, each of said coils being electrically connected to said opposed electrodes in shunt relation.

8. Apparatus for progressively heating a liquidcontaining dielectric material comprising a pair of opposed spaced elongated electrodes, one being an upper and the other a lower, means for establishing a high frequency alternating electrostatic field between said electrodes, conveyor means for advancing said dielectric material between and spaced from said electrodes, the upper electrode comprising an array of interconnected tubes having an inlet and outlet, and means for passing a heating fiuid through said interconnecting tubes with little loss of high frequency energy comprising a loop of electroconductive tubing, through which said heating fluid passes,

connected to each said inlet and outlet, each 01' said loops being electrically connected to said opposed electrodes in shunt relation.

9. Apparatus for progressively heating a liquidcontaining dielectric material comprising a pair of opposed spaced elongated electrodes, one being an upper and the other a lower, means for establishing a high-frequency alternating electrostatic field between said electrodes, conveyor means for advancing said dielectric material between and spaced from said electrodes, the upper electrode comprising an array of interconnected tubes having an inlet and outlet, and impedance means through which heating fluid is introduced to and removed from said array of tubes wit little loss of high frequency energy, said impedance means comprising a coil of electroconductive material, said coil electrically connecting said opposed electrodes at each said inlet and outlet, and at least one loop of electro- 2o conductive material provided with a shorting bar slidable along said loop electrically connecting said opposed electrodes in shunt relation.

MARTIN BATIUK. HARMON G. SHIVELY.

REFERENCE S CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Modern Plastics, June 1944, pages 116-118, 15b and 168. 

